The present invention relates to printed circuit board technology and, more particularly, to a novel method for providing insulative holes in a conductive substrate.
It is well known to use a printed circuit board for supporting electronic parts and the conductive leads interconnecting these parts. It is highly desirable to form such printed circuit boards on a substrate which has high heat-conduction capacity and high strength. Substrate materials such as steel and aluminum are preferable, as these materials are low cost and are also capable of being formed into various shapes. In particular, the use of steel as a substrate material is additionally desirable in that a steel substrate can be handled by magnetic handling means during processing. However, steel, aluminum and the like are conductive materials and must be insulated if used as a substrate. Many materials are available for insulating a conductive substrate.
It is often desirable, in the assembly of electronic systems, to provide holes in the printed circuit board, especially where large electronic components are to be mounted on a first side of the board, with leads passing through the board to an opposite side, upon which opposite side smaller components, of the chip variety and the like, may be mounted. By mounting components on both sides of a printed circuit board, wave soldering may be utilized to connect the components on both board sides in a single operation. In this manner, components which cannot withstand the temperature environment of direct soldering may be mounted. Many electronic circuit configurations, such as a touch panel in which the printed touch switchs are to be on one side of a substrate and the sensing controller electronics are to be mounted on the other side of the same substrate, will thus require holes allowing interconnection of components from one side of a substrate to the other. Therefore, a conducting substrate of material such as steel, aluminum, copper and the like, approaches the ideal substrate material for a double-sided printed circuit board, which board must, of necessity, have insulated holes passing through the substrate.